Numerous tasks, for example, cutting and cleaning various materials and surfaces, may be accomplished through the use of a stream of pressurized fluid, typically water, which is generated by an ultrahigh-pressure, positive displacement pump. Such pumps pressurize a fluid by having a reciprocating plunger that draws fluid from an inlet area into a pressurization chamber during an intake stroke, and that acts against the fluid during a pumping stroke, thereby forcing pressurized fluid through an outlet valve to an outlet chamber. The pressurized fluid in the outlet chamber is then typically collected in a manifold to be used by an operator via whatever tool has been attached to the pump for a particular task.
In order to ensure that the pump operates as desired, it is necessary to seal the pressurization chamber and prevent the leakage of fluid. One current method of sealing uses an o-ring as a low-pressure seal that in turn energizes an associated high-pressure seal. However, the o-ring is exposed to a reversing pressure differential as the pressure in the chamber cycles from a high pressure during the pumping stroke to a low pressure during the intake stroke. These pressure cycles typically dislodge or damage the o-ring, causing the sealing assembly to fail.
Another current sealing method uses an o-ring and an adjacent vent hole, as described in U.S. Pat. No. 5,111,736, assigned to Flow International Corporation, the assignee of the present invention. However, while this type of sealing assembly provides acceptable results, applicants believe that the sealing characteristics and life may be improved and that manufacturing and installation may be simplified.
A need therefore exists for an improved sealing assembly that can withstand being exposed to cycling pressures and that is simple to manufacture and install.